To answer "...or do I need to put it into a file": cron uses system() to execute cronjobs, which gives the entire line to the sh shell (for example, /bin/sh -c 'find ....'). In other words, if a command can be used inside sh, it can be used in a cronjob.
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grawityFeb 1 '11 at 12:44

-name "*" can be removed since it's implied. Recent versions of find support -exec foo {} + which gives similar results to using xargs (but -delete is all you need as grawity says).
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Dennis WilliamsonFeb 1 '11 at 14:35